Polio outbreak response, Yemen

Abstract Problem A decrease in vaccine coverage in conflict-affected areas has placed Yemen at higher risk of polio outbreaks caused by vaccine-derived poliovirus strains. Approach In response to polio outbreaks, the Yemeni health ministry and partners initiated multiple vaccination campaigns to deliver vaccines to children. We also implemented several measures to enhance communication, education, health promotion and hygiene, especially in camps for internally displaced people. Local setting In 2009, Yemen achieved polio-free status and maintained it until 2019. However, the ongoing political conflict since 2015, coupled with challenges in delivering the polio vaccine to conflict-affected areas, resulted in two polio outbreaks: 35 cases caused by vaccine-derived poliovirus strain 1 between 2019 and 2021, and 230 cases due to vaccine-derived poliovirus strain 2 between November 2021 and December 2022. Relevant changes In response to the first outbreak, by the end of 2020, we vaccinated 7.2 million children through nationwide vaccination campaigns, except in Sa’ada governorate due to a ban by the authorities. By the end of 2021, 3 800 313 children younger than 5 years had received polio vaccines. For the second outbreak, by the end of 2022, 4 463 389 vaccines had been given to children younger than 10 years, and 1 217 423 to those younger than 5 years. Lessons learnt Vaccination campaigns in conflict-affected areas with low vaccine coverage remain crucial in eradicating polio. Efforts are needed to reach vulnerable groups such as displaced populations. Advocacy, communication and social mobilization actions help ensure broader public inclusion and participation in vaccination efforts to prevent polio outbreaks.


Introduction
In 2023, Yemen is facing a threat of polio outbreaks that could paralyse more children in a country already devastated by conflict, poverty, hunger and disease.Both mass vaccination and surveillance systems have been used in the past to achieve a polio-free status.In 1998, the World Health Organization (WHO) helped launch the acute flaccid paralysis surveillance system, with the aim of quickly identifying cases and collecting samples.This initiative was accompanied by mass vaccination campaigns throughout Yemen, as part of a concerted effort to eradicate polio. 1 Yemen achieved polio-free status in 2009, and remained free of the disease until 2019.The current political conflict and war since 2015 has placed the country at a higher risk of polio and other vaccine-preventable outbreaks.
The oral polio vaccine contains three types of attenuated poliovirus strains (types 1, 2 and 3) that help people become immune to the disease.Sometimes, the attenuated virus in the vaccine can turn into a harmful strain called vaccine-derived poliovirus when not enough people get the vaccine.Vaccinederived polioviruses can then be passed to other children through faeces and the ingestion of contaminated food and water. 2 In areas with low immunization coverage, the virus can circulate for a long time and undergo genetic changes that make it more virulent and capable of causing paralysis.This is how outbreaks of polio can emerge in polio-free countries. 3,4espite the ongoing conflict, Yemen still maintains a functioning and responsive acute flaccid paralysis surveillance system. 5However, the conflict has made it difficult for health workers to reach all children for polio vaccination, particularly in remote and conflict-affected areas.In some districts in the northern governorates, all vaccination activities for polio and other vaccine-preventable infectious diseases have been banned by the local authorities. 6A study of the impact of the war on vaccination coverage demonstrated a downward trend, especially in areas where there is armed conflict. 7The problem is compounded by poor sanitation and hygiene conditions in conflict-affected areas and camps for displaced people in Yemen, posing a significant risk of outbreaks of polio and other infectious diseases. 8

Local setting
Between 2019 and 2021, Yemen reported a total of 35 cases of polio caused by the vaccine-derived poliovirus strain 1.The first case occurred in 2019, followed by 31 cases in 2020, and three cases in 2021. 9The epicentre of the outbreak was in Sa'ada governorate, an area where door-to-door vaccinations had not been allowed by the northern authorities for several years. 9 second outbreak with a different polio strain (vaccinederived poliovirus strain 2) occurred from November 2021 until December 2022.The total number of cases in this outbreak was 230, according to the Yemeni health ministry.Out of these cases, 197 were in the northern governorate, according to the Global Polio Eradication Initiative records. 10The vaccine-derived poliovirus strain 2 was identified in several governorates, including Aden, Marib, Sa'ada and Taiz. 9The total number of vaccine-derived poliovirus strain 2 cases in Yemen accounted for one third of the 634 global polio outbreaks in 2022. 11

Approach
In July 2020, the Yemeni health ministry, along with the Global Polio Eradication Initiative, started on-the-ground surveillance and implementation of prompt response measures to the Lessons from the field Polio outbreaks in Yemen Ibrahem Abduallah Beshr et al.
polio outbreaks.The measures included national and sub-national immunization campaigns using the oral polio vaccine, and environmental surveillance to monitor the circulation of polioviruses.The global initiative partners, including WHO and the United Nations Children's Fund (UNICEF), are working to overcome the challenges posed by insecurity, access restrictions, population movements, the pandemic of coronavirus disease 2019 (COVID-19) and the public's reluctance to be vaccinated. 10,12n response to the first outbreak, we conducted two vaccination campaigns.The first round took place in July 2020, covering 10 governorates.The second round was in November 2020 in the north, and December 2020 in the south.For the second outbreak, three campaigns were initiated in the 12 southern governorates.The first two rounds took place in February and March 2022, while the third campaign occurred in May.In March 2023, the first round of the polio campaign was delivered in the southern governorates; however, in the northern governorates, where 65% of the population resides, vaccination outside of health facilities is still suspended by the northern authorities.
We used many strategies at every level to reach the target of vaccinating all children younger than 5 years.UNICEF, WHO and their partners implemented advocacy, communication and social mobilization actions nationwide several days before the start of the polio vaccination campaign.These actions were designed to sensitize and educate the public, raise awareness, reduce vaccine hesitancy, and to ensure broader public inclusion and participation. 6,12,13The advocacy, communication and social mobilization actions included meetings with representatives of government and the community, and religious leaders.Religious leaders held sessions at mosques, community meetings, women's gatherings and schools.These sessions helped to promote polio vaccination, hygiene awareness and sanitation practices.We also used vehicles with megaphones, as well as numerous posters and banners at strategically placed locations. 6,12,13To enhance communication and support, community volunteers created mobile phone message groups (WhatsApp Messenger, Meta Platforms, Menlo Park, United States of America) to help with communication and support.The health ministry and UNICEF set up dedicated telephone numbers to allow the public to connect with healthcare professionals with enquiries about polio disease, vaccines and various health-related topics. 6,12,13e also implemented the water, sanitation and hygiene programme to improve water safety.The programme staff delivered gender-specific latrines and hygiene kits to camps for internally displaced people, which is the most vulnerable population.They also contributed to the rehabilitation and maintenance of sanitation systems across the country.Furthermore, they aided in the repair of wastewater treatment plants.In terms of safe water supply, the programme staff helped deliver safe drinking water to camps of internally displaced people; and expanded water, sanitation and hygiene services to both rural and urban areas.Staff provided chlorination tablets, cleaning kits and water filters to camps and households as well.Additionally, the staff assisted in the rehabilitation and maintenance of multiple water collection points and systems (pumping stations and wells, water harvesting systems, communal points, pipelines, trucking and storage tanks). 6,12,13

Relevant changes
In response to the first outbreak, by the end of 2020, we were able to vaccinate 7.2 million children through two nationwide vaccination campaigns, except in Sa'ada governorate due to a ban by the authorities.In 2021, 3 800 313 children younger than 5 years had received polio vaccines.UNICEF has reported that the two campaigns reached 96% and 93% of the target population, respectively. 12or the second outbreak, by the end of 2022, 4 463 389 vaccines had been given to children younger than 10 years, and 1 217 423 to those younger than 5 years, an estimated 102% of the target population in the southern governorates.The ban by the authorities on vaccinations outside of health-care facilities persisted in northern governorates, despite all the efforts of WHO and UNICEF.The authorities continue to prohibit vaccination activities for polio and measles in northern governorates.An outbreak of measles has also been documented. 6,12,13ommunity volunteers reached 2 110 635 people through house-tohouse visits to deliver vaccines and motivate households if there was vaccine hesitancy.A total of 11 television channels and 16 radio stations provided mass media coverage, broadcasting campaign messages and highlighting the significance of vaccination.

Lessons learnt
Despite these renewed efforts and the successful campaign in the southern governorates, there are still political challenges and gaps in polio prevention in Yemen.The northern governorates are governed by the Houthi regime, which gained control after a coup in 2015.The official government has control of the south, but has no jurisdiction over the northern governorates which are the most conflict-affected areas.The northern authorities have continued to suspend vaccination activities in certain districts, putting these vulnerable communities at a higher risk of another polio outbreak.UNICEF and WHO still hold talks and advocate for approval to begin vaccination campaigns in conflictaffected areas.The lengthy bureaucratic authorization processes imposed by the governing authorities in the north cause delays in responding to polio outbreaks in a timely manner.Additionally, there are areas that are hard to reach, with limited access to health facilities and resources (Box 1).The only way to deliver vaccines in these areas is through primary health facilities, but no doorto-door vaccination delivery has been approved.UNICEF and WHO also continue to provide support to the primary health teams in these areas, and assist in conducting outreach programmes.

Box 1. Summary of main lessons learnt
• Advocacy, communication and social mobilization including grassroots communitydrivenactions, were a crucial part of two successful nationwide polio vaccination campaigns.• Lengthy bureaucratic authorization processes caused delays in responding to polio outbreaks in a timely manner.• Limited access to health facilities and resources in conflict-affected areas, and prohibition of polio vaccination by governing authorities in some areas, created gaps in vaccination coverage.
Yemen is a water-scarce country, and the ongoing conflict has exacerbated the situation.Despite the efforts of the water, sanitation and hygiene programme to improve sanitation and ensure a safe water supply, we have underachieved in this area due to a funding gap, according to reports by UNICEF. 6dditionally, the sanitation infrastructure in the country is below standard and requires improvement. 6Activities such as hygiene promotion, and direct engagement with communities are still banned by the governing authorities in the northern governorates. 6accination campaigns remain a crucial part of eradicating polio.Advocacy, communication and social mobilization actions emphasize the importance of a multifaceted approach, including community-driven actions, to effectively combat and control polio outbreaks.The recent polio outbreaks in Yemen serve as a reminder that in any area where vaccine coverage is low, it is only a matter of time before an outbreak occurs.Our experience also highlights the urgency of eradicating polio globally, and ensuring that every child is protected from this preventable disease.■ Polio outbreaks in Yemen Ibrahem Abduallah Beshr et al.